1. Field of the Invention
The present invention relates to an image copying apparatus of a type that is provided with a feeding mechanism for feeding an original to be copied and image receiving medium synchronously with each other. More particularly, the present invention relates to a facsimile machine of a type that has a copy function and that is provided with a feeding mechanism for synchronously feeding an original and image receiving medium.
2. Description of the Related Art
There has been known a conventional facsimile machine of a type that is provided with only a single motor which is use for feeding both an original and image receiving medium. The facsimile machine includes reading means for reading an original image on the original which is being fed by the single motor and for producing an original image data representative of the original image. The facsimile machine further includes recording means for receiving image data and recording, in response to the image data, an image on image receiving medium which is also being fed by the single motor. For example, the recording means is a thermal head, and the image receiving medium is a heat-sensitive paper. The facsimile machine has an image transmission function and an image receiving function. In the image transmission mode, the reading means reads out the original image to produce the original image data which is then encoded before being transmitted to a remote facsimile machine. In the image reception mode, the facsimile machine receives image data transmitted from a remote facsimile machine and decodes the received image data. The recording means records, in response to the decoded image data, an image on the image receiving medium.
Generally, the facsimile machine further has an image copy function which is attained by combination of the above-described image transmitting function and image receiving function. More specifically, in the image copy mode, the facsimile machine controls the reading means to read out the original image on the original being fed by the motor to produce the original image data, transfers the original image data to the recording means, and allows the recording means to record, in response to the original image data, the original image on the image receiving medium. Since the single motor is used for feeding both the original and the image receiving medium, the original and the image receiving medium are fed synchronously with each other. In the image copy mode, therefore, it is necessary that the recording means should perform its recording operation synchronously with the reading operation of the reading means. In order to synchronize the recording operation and the reading operation, in the conventional facsimile machine, the thermal head is designed to include: a shift register for receiving the original image data in serial form and for outputting the original image data in parallel form; a latch memory for receiving the original image data from the shift register and for temporarily storing them; a drive circuit connected to the latch memory for driving a thermal element array, according to the original image data stored in the latch memory, so as to selectively heat the thermal element array to thereby record the original image on the heat-sensitive paper; and the thermal element array.
In the copy mode, the thermal head of the above-described structure performs its recording operation synchronously with the reading operation, as will be described below.
While the motor synchronously feeds the original and the heat-sensitive paper by a line distance, the reading means reads out one line (which will be referred to as a "noted line," hereinafter) of the original image, and produces the original image data for the noted line. The reading means transfers, in serial form, the original image data for the noted line to the shift register of the thermal head. After all the original image data for the noted line have been completely transferred to the shift register, they are transferred in parallel form from the shift register to the latch memory.
The thermal head then reads out the next line of the original image which is positioned next to the noted line, and produces the original image data for the next line. The thermal head then transfers the thus produced original image data to the shift register. While the data for the next line is thus being read and transferred to the shift register, the drive circuit of the thermal head selectively heats the thermal element array according to the data stored in the latch memory. As a result, the original image of the noted line is recorded on the heat-sensitive paper using well-known method. In this way, one line is recorded while the next line is read. That is, the recording and reading operations are performed simultaneously or synchronously.
The above-described conventional facsimile machine has, however, a problem in that the latch memory provided in the thermal head is expensive and therefore increases the production cost of the entire facsimile machine.